The present invention relates to a mixing device comprising a swing arm for receiving a mixing capsule within securing arms whereby at least one securing arm is movably supported at the swing arm so that the two securing arms can be moved relative to one another.
Such a mixing device is, for example, known from U.S. Pat. No. 3,749,371. This document shows a mixing device with two spaced apart securing arms which support the mixing capsule that contains the dental material to be mixed.
Mixing capsules for dental materials are manufactured with different dimensions, and the respective mixing devices therefore require a spring-loaded support within the swing arm. Since the capsules are subjected to very high acceleration forces in order to ensure a sufficient mixing action of the amalgam, the prongs of the mixing device in the known device are thus subjected to high loads so that they must be embodied with sufficient stability in order to prevent breakage during operation. This requires that for the insertion of the capsules relatively great actuating forces must be expended.
Furthermore, mixing devices have been suggested in which the mixing capsules are received in a closed space and are thus securely contained. In this context, it has been suggested to introduce by movement of one of the securing arms a canting action in order to ensure a safe securing of the mixing capsule by canting. In this suggested solution it is especially disadvantageous that the canting can act only on one side so that during the return swing movement the canting force is greatly reduced, if not eliminated. The canting elements are thus subjected to great changing loads. The resulting corresponding wear can not ensure safe canting over an extended period of time.
A further example of such a mixing device is known from U.S. Pat. No. 4,074,900 in which the mixing capsule is secured in a closed chamber and a locked by a fork in the mixing position. Even though this solution exhibits reduced wear, it has not found acceptance because it requires a very stable embodiment of the securing arm similar to the aforementioned solution.
Since the securing arm swings or pivots, it is therefore not only necessary to increase the drive forces in order to ensure the same mixing result. Also, a stronger swinging load of the drive device results so that correspondingly strong oscillations, undesirable in dental practices, are introduced into the support of the mixing device.
Accordingly, in general, the comparatively light-weight spring-loaded mixing devices or forks have found greater acceptance whereby preferably hard and at the same time light-weight spring steel has been used for the mixing forks. A lateral introduction of the capsule is generally preferred. An example for such a solution is known from German Patent 41 06 388.
It is therefore an object of the present invention to provide a mixing device of the aforementioned kind which, in comparison to the prior art mixing devices, introduces a reduced amount of oscillations into the support for the mixing device but still ensures easy operation with secure hold of mixing capsules of different sizes.